The drivers of two vehicles were racing in the southbound lanes near Washington Boulevard when one of them lost control of his vehicle and veered into a UPS big-rig, authorities said. The UPS truck slammed into the center divider, then flipped over into the northbound lanes and collided with several oncoming vehicles, causing an explosion, said Sgt. Luis Mendoza of the California Highway Patrol.

Dealio Lockhart, 35, of Whittier, identified as one of the suspected street racers, was arrested at the scene and will face vehicular manslaughter charges, according to a statement from the California Highway Patrol.

CHP Officer Alex Rubio said Lockhart admitted to investigators that he had been racing.

Lockhart, who was driving a Dodge Challenger, was racing the driver of a Dodge Charger at the time of the crash, authorities said. Lockhart tried to swerve around a slower vehicle, applied his brakes and lost control of his car, crashing into the UPS truck and triggering the fiery pileup.

The male driver of the big rig and two women in the Nissan died at the scene, CHP Officer Tony Polizzi said.

The driver of the Charger remains at large.

"Unfortunately there's not a lot of leads, not a lot of information," Mendoza said about the search for the second car.

The CHP said that alcohol and drugs were not believed to have been a factor in the crash.